Manufacture of sulfur compounds



March 15, 1960 Filed March 18, 1958 INVENTOR.

ROBERT C. BUTLER ATTORNEY MANUFACTURE OF SULFUR COMPOUNDS Robert C. Butler, El Dorado, Ark., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Application March 18, 1958, Serial No. 722,219

7 Claims. (Cl. 260-609) This inventionrelates to the manufacture of organic sulfur compounds and more particularly to the preparation of alkyl mercaptans.

The synthesis of alkyl mercaptans by the addition of hydrogen sulfide to olefinic materials in the presence of a catalyst is well known in the art. The more significant processes of commercial importance generally utilize rather extreme reaction conditions. A process characterized by a rapid and complete reaction under relatively mild temperature conditions at substantially atmospheric pressures has not becomea commercial reality. It is an object of this invention to provide such a process. Further objects will become apparent from the description of this invention.

It has now been discovered that excellent yields of alkyl mercaptans can be obtained by the reaction of an olefin and hydrogen sulfide in the presence of boron trifluon'de as the catalyst and a small amount of water as a catalyst activator at mild temperatures with the substantially complete single pass reaction of H S. The process comprises passing H 8 and BF into a liquid olefin in a manner such that the BE, is mixed with the olefin before contact of the BF with the H stream feed, said BF, being employed in the molar ratio of H S:BF of from about :1 to about 100:1 and the H 8 containing water in the molar ratio of H O:BF of from about 05:1 to about 2:1.

The drawing is a schematic representation of a reaction system particularly suited to the process of this in vention.

In this system, the olefin is placed in the reactor 1, H 8 is passed through H O scrubber 2 picking up H O and the wet H 3 then passed into the reactor through diffuser 3. BF is introduced into the reactor through diffuser 4 placed at a point below difiuser 3 to permit BF; to mix with the olefin before contact with wet H S. The crude mercaptan is removed from the reactor through line 5 into tank 6 which contains H O to quench the catalyst. The crude mercaptan layer is allowed to separate from the water and is then passed through a glass wool coalescer 7 to remove any entrained H O. The crude material may then be further purified, as by distillation, if desired.

The following examples illustrate this invention:

Example I 7 the end of 25 minutes, the reaction mixture was quenched in water and the crude product was found to contain The process set forth in Example I was repeated with the H S feed by-passing the water filled scrubber. The product contained only 4.2% SH and a significant quantity of H 8 passed through the olefin unreacted.

Example III A 200 ml. sample of tetrapropylene was placed in a glass tube and a mixture of 98% H 8 and 2% BF was bubbled through the olefin at the rate of one minute. was quenched by pouring into water. The crude product recovered was found to contain 6.8% SH representliter per 1 ing 42% dodecyl mercaptan. Only- 16% of the H 8 fed reacted to yield the mercaptan, the remainder. of the the reaction conditions.

H S passing through the olefin unreacted. The temperature of the reaction mixture was 25C. initially and rose to 50 C. during the run.

Example IV Example V The procedure set forth in Example I is repeated using as the olefin a natural gasoline fraction containing about 15 weight percent triisobutylene. An excellent yield of triisobutyl mercaptan is obtained with substantially complete single pass consumption of H 5 fed.

Example VI The procedure set forth in Example 'I is repeated using cyclohexene as the olefin. An excellent yield of cyclohexyl mercaptan is obtained with substantially complete single pass consumption of the H 8.

A comparison of the results obtained in Examples I to III clearly illustrates the improvementsobtained using the process of this invention. The process is subject to some variations. The reaction temperature can be maintained in the range of from about 20 C. to about C. and preferably between about 40 C. and 60 C. The reaction is conveniently carried out at atmospheric pressure although pressure above or below atmospheric can be used if desired in a particular case.

In the practice of this invention, it is essential that BF be mixed with the olefin before it is contacted with WetI-I S. This can be accomplished by the continuous method of Example I or the BF separately dispersed in the olefin before any H 8 feed is introduced. Any other convenient method can be employed for this purpose.

The olefins which may be reacted with H S in accordance with this invention include those which contain one or more olefinic unsaturations between two aliphatic carbon atoms regardless of the class or characteristic of the compound containing such linkage. Such hydrocarbons can also contain substituent groups which are inert under Examples of olefins which can be used in this process are ethylene, propylene, butylenes, pentenes, hexenes, cyclohexene, l-methylcyclohexene-l; propylene trimers, propylene tetramers and propylene pentarners; diisobutylenes such as 2,4,4-trimethylpentene-l, and 2,4,4-trimethylpentene-2, octene-l and -2; tria isobutylenes such as 2,2,4,6,6-pentamethylheptene-3, do-

decane-l and -2, 2-n-pentyl-4,4-dimethylpentene-l, 2,4,

4,6,6-pentamethylheptene-2 and -1; 1,4-diphenylbutene-2;

Patented Mar. 15, 1960 At the end of one hour, the reaction mixture- F. cut of heavy polymer from tin is a propylene polymer.

tetraisobutylenes such as cetene-l and -2; and their I honiologues and analogues. -.The olefins can be used as such or can be mixed with inert hydrocarbons.

What is claimed is:

l. A process for preparing alkyl mercaptans which comprises reacting at a temperature in the range of from about 20 C. to about 80 C. an olefin in the presence of BF with H 8 containing H O in a manner such that the 3P is mixed with the olefin before contact of the BE; with the H 8, said BF being employed in the molar ratio of H szBF of from about 10:1 to about 200:1 and the H 8 containing water in the molar ratio of H ozBF of from about 0.5:1 to about 2:1.

2. A'process as" described in claim l wherein the ole- 3. A process'as described in claim 2, wherein the olefin is a propylene tetrarner.

" .4. A process for preparing alkyl mercaptans which comprises separately passing H and BE; into a liquid olefin at a temperature' in the range of from about 20 C. to about 80 C. in amanner such that the BE, is mixed withthe olefin'before contact of'the BF; with the H 5 stream .feed, said BF wbeing employedin the molar ratio of H szBF of from about 10:1 to about 100:1 and the H 8 containing water in the molar ratio of H O:BF of from about 0.5:1 to about 2:1.

5. A process as described in claim 4, wherein the olefin is a propylene polymer.

6. A process as described in claim 5, wherein the olefin is a propylene tetramer.

7. A process for preparing alkyl mercaptans which comprises reacting ata te'mperaturein the range of from about 40 C. to about C. an olefin in the presence of BF with H 8 containingH O in a manner such that the B1 is mixed with the olefin before contact ofzthe BF with the H 5, said BF being employed'in the molar ratio of HzSiBFg; of from about 10:1 to about :1 and the H 3 containing water in the molar ratio of H OzBF or from about 0.5:1 to about 2: 1:

I ,ltefi erences'Cited in the file of this patent UNITED STATES PATENTS 2,481,583 Fenn et a1. Sept. 13, 1949 

1. A PROCESS FOR PREPARING ALKYL MERCAPTANS WHICH COMPRISES REACTING AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 20*C. TO ABOUT 80*C. AN OLEFIN IN THE PRESENCE OF BF3 WITH H2S CONTAINING H2O IN A MANNER SUCH THAT THE BF3 IS MIXED WITH THE OLEFIN BEFORE CONTACT OF THE BF3 WITH THE H2S, SAID FB3 BEING EMPLOYED IN THE MOLAR RATIO OF H2S:BF3 OF FROM ABOUT 10:1 TO ABOUT 100:1 AND THE H2S CONTAINING WATER IN THE MOLAR RATIO OF H2O:BF3 OF FROM ABOUT 0.5:1 TO ABOUT 2:1. 